Use precisepy3k instead of precise3k.

* manifests/site.pp: Unfortunately node names like precise3k-1
match the existing node name pattern precise-?\d+.* and end up with
the precise.slave.openstack.org shared puppet cert as a result.
Switch to precisepy3k which won't have this unintended side effect.

Change-Id: I2a530b0e19af769700e85f9060c2cbd8592eef1d
Merge "Use precisepy3k instead of precise3k."